[M-IS14] 南大洋・南極氷床が駆動する全球気候変動

[MIS14-P07] 東南極における大気硫酸の硫黄安定同位体組成の季節変動と大気硫黄循環への示唆

*石野 咲子¹、服部 祥平¹、Joel Savarino²、Michel Legrand²、Susanne Preunkert²、Bruno Jourdain²、Francis Albarede³、Emmanuelle Albalat³、吉田 尚弘^1,4 (1.東京工業大学物質理工学院応用化学系、2.グルノーブル大学/CNRS、環境地球科学研究所、3.リヨン高等師範学校（LGL-TPE）、4.東京工業大学地球生命研究所)

キーワード：硫黄同位体分析、硫酸エアロゾル、南極

Atmospheric sulfate in Antarctica is produced mainly from a marine biogenic sulfur compound, dimethyl sulfide. They are therefore a subject of study related to the linkage between marine biogenic activity and climate. We investigate year-round observations of sulfur isotopic compositions of atmospheric sulfate (SO₄²⁻) at inland (Dome C) and coastal (Dumont d’Urville) sites in East Antarctica to quantify the relative importance of marine biogenic (mb) and non-marine biogenic (nmb) SO₄²⁻ for the Antarctic atmospheric sulfur cycle. The δ³⁴S values of non-sea salt sulfate showed clear seasonal variations with summer maxima and winter minima, and showed homogeneity between inland and coastal sites throughout the year. This result suggests that the isotopic fractionation through chemical reactions during transportation from coastal to inland areas insignificantly affects the observed δ³⁴S_nss values. The observed δ³⁴S_nss values are controlled mainly by the relative importance of mb-SO₄²⁻ and nmb-SO₄²⁻. This finding, in conjunction with the SO₄²⁻ records in Antarctic ice cores, will open a perspective implying the increased relative importance of nmb-SO₄²⁻ during glacial periods. We also found a significant increase in nmb-SO₄²⁻ concentrations in November, especially for the inland site. This nmb-SO₄²⁻ increase is correlated with the ²¹⁰Pb concentration, suggesting the existence of long-range transport of continental nmb-SO₄²⁻ from lower latitudes to the Antarctic inland. Identification of the sources of those nmb-SO₄²⁻ will be a key step for elucidation of the linkage between Antarctic atmosphere/climate and environmental changes at lower latitudes from the past through the future.